The present invention relates to a method for enhancing pesticidal efficacy with dicarboxylic acids. More particularly, the present invention relates to a method of enhancing the herbicidal effectiveness of glyphosate concentrates and tank mix formulations optionally containing one or more surfactants through the addition of a dicarboxylic acid or another component which increases EPSPS enzyme inhibition by glyphosate, cell membrane permeability or hydroxyproline-rich glycoprotein expression.
Polycarboxylic acids have been added to glyphosate compositions. For example, Prill et al. WO 92/12637 discloses water soluble tablets containing glyphosate acid, an acid acceptor such as sodium oxalate, and an optional anionic surfactant. The acid acceptor is said to solubilize glyphosate acid through glyphosate salt formation upon exposure to water.
U.S. Patent Application Pub. No. US2002/0049140 A1 discloses herbicide tablets containing 20 wt % of glyphosate acid, 10 wt % surfactant, a base such as ammonium hydrogen carbonate or carbonate, and 11 wt % oxalic acid. Upon exposure to water the base reacts with the organic acid to generate carbon dioxide and improve tablet disintegration via effervescence.
U.S. Pat. No. 5,948,421 to Okano et al. describes aqueous concentrate formulations containing 37.8 wt. % (a.e.) isopropylamine glyphosate, chelating agents including 1.9 wt % (a.e.) potassium oxalate, and 8-10% surfactant.
U.S. Pat. Nos. 5,795,847 and 6,180,566 to Nielsen et al. disclose an aqueous suspension containing solid glyphosate acid, a synergistic amount of a dissolved electrolyte, most preferably ammonium sulphate, and surfactant. Optionally polycarboxylic acids may be added as pH buffers and to activate surfactant amino groups.
WO95/17817 to Hasabe et al. discloses an enhancer composition for agricultural chemicals which comprises at least one nitrogen containing surfactant and a chelating agent and the use of said composition in tank mixes with the isopropylamine salt of glyphosate in a weight ratio of 4.8:1 glyphosate to oxalic acid on an a.e. basis.
Polycarboxylic acids have been used as chelators to enhance glyphosate efficacy in tank mix compositions. For example, D. J. Turner reported in Butterworths (1985), at pages 229-230, that 2% concentrations of polycarboxylic acids in glyphosate (Roundup®) tank mixes gave efficacy enhancement. Further, Research Disclosure publication number RD15334, Industrial Opportunities Ltd., Homewell-Havant-Hampshire P09 1EF, United Kingdom (January 1977), disclosed that glyphosate tank mixes formulated with water containing calcium and/or magnesium ions in concentrations greater than 200 ppm (hard water) had diminished herbicidal activity. Herbicidal activity was restored by adding oxalic acid to the tank mix in weight ratios to glyphosate of between about 1:10 to about 10:1.
U.S. Pat. No. 5,863,863 to Hasabe et al. teaches tank mix and liquid concentrate formulations containing IPA glyphosate and oxalic acid salts in a weight ratio of 15:1 on an a.e. basis.
U.S. Pat. No. 5,525,576 to Medina-Vega et al. discloses a process for preparing a seed hull extract containing a mixture of polycarboxylic acids for use as a herbicide assimilation agent. 0.25% of the extract was added to tank mixes containing the trimethylsulfonium (TMS) salt of glyphosate (sold commercially as Touchdown®) or the isopropylamine (IPA) salt of glyphosate (sold commercially as Roundup®). U.S. Pat. No. 5,436,220 to Hickey teaches an efficacy enhancing formulation comprising a seed hull extract containing tricarboxylic acids and Roundup® herbicide, with glyphosate application rates of 64 to 191 g/ha in combination with 82 g/ha of a seed hull extract containing about 5 wt % tricarboxylic acid.
U.S. Pat. Nos. 5,849,663, 6,093,679, and 6,008,158 describe spray compositions containing TMS or IPA glyphosate, oxalic acid or potassium or diethyl oxalate, and surfactant in a weight ratio of glyphosate to oxalic acid of 4:1 to 11:1 on an a.e. basis.
U.S. Pat. No. 6,218,336 to Coleman discloses tank mixes containing up to 1.25 wt % Roundup® Ultra IPA glyphosate and 2.5 wt % of succinic, tartaric or malic acids or their ammonium salts. Sylgard 309® (ethoxylated organosilicone) and Emsorb 6900® (polyoxyethylenated sorbitol ester) surfactants may be added to the tank mixes.
It would be desirable to enhance the efficacy of solid or liquid glyphosate concentrates. Greater efficacy affords lower application rates of the herbicide to achieve the same degree of weed control. Application of less herbicide is cost effective to the consumer since less product provides equivalent weed control. Moreover, such an enhanced efficacy formulation is environmentally responsible because packaged volume is reduced, less storage space is required, shipping cost savings may be realized, and most importantly, environmental burden is minimized through reduced application rate requirements. As will be clear from the disclosure that follows, these and other benefits are provided by the present invention.